Can A CT Scan Be Conclusive For Brain Damage Or Bleeding?

This case is now focused on cardiac issues: my friend is a 69 yr old male. three months ago he started to complain about hip and back pain. He was treated only for muscular/skeletal symptoms. His condition prevented him from his regular exercise and became weaker and less mobile. about six weeks ago, a infectious disease physician diagnosed my friend with staphylococcus lugdenensis. He was placed on antibiotics. after four weeks of infusion treatments, he was not demonstrating sufficient improvement. His antibiotic was changed and it was recommended that he have spinal surgery as the MRI indicated he deposit. two weeks ago surgery was initiated to drain, deride and fuse two vertebrae. About one hour into the surgery, the patient suffered a V-Fib, was resuscitated and the operation ended. He was treated with hypothermal therapy, certain medicines, placed on a ventilator. Two days later, he was able to breath on his own, but for the first day was unresponsive. Two days after that, he was conscious and conversing with his brother, albeit weakly when he suddenly stopped and apparently passed out. The hospital staff resuscitated him, he was taken to a surgical unit and had a balloon angioplasty, He was the taken to the CCU and placed him on a ventilator, administered medications, oxygen, etc. He had a CT scan of his brain which was negative. This occurred five days ago. He has been on and off the ventilator and is able to breath on his own for short periods. Apparently, his heart output is ~25% of normal. The doctors have told the family they are not overly concerned about the low output and are treating him as necessary for fluid build ups. He has good color, but remains unconscious and unresponsive. He has underlying diabetes under control with medications and A-fib treated with cumin, which may explain why the surgeons could not place a stent into the heart. He continues to receive the antibiotics medication for his infection. He had no previous history of any cardiac events. I don t have contact with his medical team and his wife, my contact, does not have specific medical information. Since he has been my best friend since high school, I am very worried. Is it normal for this unresponsive, unconscious state to follow this confluence of events? Is the CT scan a reliable test for brain damage or bleeding? I don t understand why the heart, if it is not damaged, is underperforming so greatly. And, if the brain is not damaged, i don t understand the unresponsive state. Would you opinion include the possibility that he might sill regain consciousness? Any other comments will be appreciated.